An INS-TOSCA Study on Adsorption-induced Vibrational Features of Methylene Blue and Methyl Orange on TiO2-modified Mesoporous Silica

The growing adoption of synthetic dyes in the textile market, wherein approximately 700,000 tons are consumed per year, has brought about grave environmental issues through the release of toxic azo dyes such as methylene blue (MB) and methyl orange (MO). Titanium dioxide (TiO2) is known to be rich in photoreductive power to breakdown organic pollutants, but this performance is hampered due to limited surface area and accelerated recombination of charges. The combination of TiO2 with mesoporous silica offers the potential to suppress agglomeration of nanoparticles and facilitate effective mass transfer. Preliminary findings indicate that the mesoporous silica/TiO2 demonstrate higher removal capacity as well as quicker kinetics compared to the pure materials, due to adsorption-photocatalytic synergy. However, molecular-scale processes governing such synergistic interaction are still obscure. Accordingly, this research advocates the adoption of inelastic neutron scattering (INS) on the TOSCA to investigate vibrational states of MB and MO adsorbed onto TiO2-functionalized mesoporous silica. The spectra will be used to illuminate adsorption-related vibrational shifts, adsorption characteristics, as well as intermediates during the process of degradation, gaining unprecedented understanding of dye surface interaction. The results will lay the groundwork towards the development of the next generation of hybrid TiO2-based systems with enhanced environmental remediation performance.